Republican activists at a national gathering are defending New Jersey Gov. Chris Christie but also are saying it's far too soon to grant him presidential frontrunner status. At the same time, a senior Christie adviser says the governor already has overcome the worst of his challenges, though federal prosecutors have issued subpoenas to his recent campaign and Democrats are pressing their abuse-of-power accusations. Christie's popularity has fallen amid revelations that senior members of his administration helped create massive traffic jams, apparently to exact political retribution against a Democratic mayor.